Differences in calculated percentage improvement versus patient-reported percentage improvement in pain scores: a review of spinal cord stimulation trials.

INTRODUCTION: Spinal cord stimulation is frequently used for the treatment of intractable chronic pain conditions. Trialing of the spinal cord stimulator device is recommended to assess the patient's response to neurostimulation before permanent implantation. The trial response is often assessed by Numeric Rating Scale changes and patient-reported percentage pain improvement. Using number rating scale changes between prespinal and postspinal cord stimulation trial, a calculated percentage pain improvement can be obtained. The aim of this study was to assess the difference between calculated and patient-reported percentage improvement in pain scale during spinal cord stimulation trials. METHODS: This study was a retrospective single center review of all spinal cord stimulation trials from January 1 2017 to July 1 2019. A total of 174 patients were included. The paired t-test was used to compare numeric pain scores obtained prestimulation versus poststimulation. The mean difference between methods (patient-reported minus calculated) was compared with zero using the 1-sample t-test. Lin's concordance correlation coefficient was computed with a 95% CI, calculated using Fisher z-transformation; and a bootstrapping approach was used to compare the concordance correlation coefficient between groups. In all cases, two-tailed tests were used with p<0.05 considered statistically significant. RESULTS: Based on prestimulation and poststimulation numeric rating scale scores, the mean±SD calculated percentage improvement in pain scale was 54±28. The mean±SD patient-reported percentage improvement in pain scale was 59±25. The overall 95% limits of agreement for the two methods are -30% to +41%. The overall concordance correlation coefficient was 0.76 (95% CI 0.69 to 0.81). CONCLUSION: Although the two methods are highly correlated, there is substantial lack of agreement between patient-reported and calculated percentage improvement in pain scale, suggesting that these measures should not be used interchangeably for spinal cord stimulator trial outcome assessment. This emphasizes the need for improved metrics to better measure patient response to neuromodulation therapies. Additionally, patient-reported percentage improvement in pain was found to be higher than calculated percentage improvement in pain, potentially highlighting the multidimensional experience of pain and the unpredictability of solely using Numeric Rating Scale scores to assess patient outcomes.

Spinal Cord Stimulation for Neuropathic Pain Treatment in Brachial Plexus Avulsions: A Literature Review and Report of Two Cases.

BACKGROUND: At least 50% of individuals who suffer a brachial plexus avulsion (BPA) will develop chronic pain, frequently more debilitating than their functional limitations. Similar to other neuropathic pain states, BPA pain is often refractory to pharmacological agents. Despite spinal cord stimulation (SCS) first being used for BPA in 1974, there have been no published literature reviews examining the current evidence of SCS for the treatment of neuropathic pain following BPA. In addition to a clinical review of the literature for this indication, we also share our experience with high-frequency SCS (HF-SCS) for BPA-related pain. METHODS: MEDLINE and EMBASE databases were searched. All published articles including at least one BPA individual treated with SCS for pain treatment were included. RESULTS: The initial search identified 288 articles, of which 13 met inclusion criteria for a total of 41 patients. These patients were primarily male and underwent SCS with reported improved pain scores. CASE REPORTS: HF-SCS leads were percutaneously placed in two male patients who suffered BPA from traumatic injuries. At follow-ups of 13 and eight months, respectively, both patients continued to report an improvement in their pain. CONCLUSIONS: Despite published reports showing benefit for pain control in patients with BPA, the overall low quality, retrospective evidence included in this review highlights the need for a rigorous prospective study to further address this indication.